Risk Assessment Outline

For Use in Preparing Risk Analyses

For Biotechnology-Derived Products

The Center for Veterinary Biologics

USDA/APHIS/VS

Risk assessment may be defined as determination of the likelihood of an adverse event occurring 

and the consequences if that adverse event occurs. An adverse event is defined as a safety 

hazard to animals, public health, or the environment. A safety hazard is defined as a danger, 

risk, or peril. There may be an absence of predictability associated with an adverse event.

When submitting a Risk Analysis to the Center for Veterinary Biologics (CVB) for prelicense 

evaluation of a biotechnology-derived product, the Risk Analysis should contain the most current 

version of the Summary of Information Format (SIF) and a Risk Assessment (RA) [Table 1]. 

The CVB requires that the applicant conduct a RA based on safety characteristics of the vaccine. 

The safety characteristics are based on empirical data and established scientific facts. The 

completion of a risk assessment requires that the vaccine microorganism is properly 

characterized. This information is included in Section III of the CVB SIF.

Risk Assessment Outline

A. Hazard Identification

 Hazard identification consists of identifying all possible adverse events to animal safety, 

 public health safety, and environment safety relative to recommended use of the product.

1. Animal Safety

a. Target animal safety

 

 The safety of the experimental biologic in the target animal species is 

 thoroughly evaluated. Several standard safety studies are available for 

 veterinary vaccines. Thus, the safety of the experimental biologic in the target 

 animal is based on direct scientific evidence.

i. Vaccination

 The safety of the experimental biologic in the target animal species 

 should be established. Adverse systemic reactions should be 

 documented and described. Certain viruses are associated with 
 immunosuppression, e.g., feline leukemia and canine distemper. The 

 impact of live vaccines that contain this type of virus should be 

 thoroughly evaluated. 

ii. Vaccination/Challenge

 The safety of the experimental biologic when the target host is exposed to 

 the challenge wild-type microorganism should be established. Although 

 the induction of a specific immune response is essential for protection, its 

 function can have adverse consequences, such as antibody-complement 

 interaction, immune complex formation, and the generation of 

 autoantibodies directed against normal tissues that have not themselves 

 been infected. These examples demonstrate the importance of evaluating 

 vaccine safety in the context of a challenge. Thus, experimental designs 

 for immunogenicity studies should not be limited in their focus by 

 concentrating exclusively on the efficacy of the product; the focus should 

 be extended to include provisions for evaluating safety.

iii. Reversion to virulence

 The inability of attenuated vaccine strains to revert to virulence should 

 be established. In some cases, it may be determined that the vaccine 

 microorganism does revert to virulence, but that the level of virulence 

 is acceptable. This usually requires that the pathophysiology of the 

 vaccine microorganism be thoroughly evaluated to ensure that the

 margin of safety will be acceptable for the target host.

iv. Purity testing

 Contaminants in veterinary biologics are unacceptable. However, new 

 techniques are providing levels of sensitivity not previously attainable. 

 For instance, polymerase chain reaction (PCR) analysis may identify 

 previously undetected contaminating retroviruses. In those cases, 

 extraneous agents should be fully characterized. For example, it should 

 be established that: 1) the detected agent is present in a replication 

 competent form and is not just a genomic segment detected by PCR; 2) 

 the agent is not a pathogen for the target host; 3) the agent cannot 

 propagate in the target host; 4) the agent has no oncogenic properties; 

 5) the final product does not contain an infective dose of the extraneous 

 agent(s); and 6) the margin of safety is sufficient so that the product will 

 be safe when used in accordance with label recommendations.

v. Effect of gene manipulation on pathogenicity

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 Information on the genetic profile of the vaccine microorganism can 

 contribute significantly to our understanding of its safety characteristics. 

 This is not only applicable to genetically-engineered microorganisms, 

 but to organisms that have been attenuated by conventional methods. 

 The purpose is not to regulate the process used to construct the vaccine 

 microorganism, but to identify potential safety hazards associated with 

 any genetic modifications.

 In the case of ‘attenuated’ vaccines, the actual attenuation may be the 

 result of a single base pair substitution and the potential for reversion to 

 virulence may be high. 

 Genetic markers may provide the means with which to monitor the 

 dispersal or establishment of the vaccine microorganism upon its 

 release in the environment. In some cases, genetic markers actually 

 define the safety characteristics of the vaccine microorganism, as with 

 aroA deletion mutants. The attenuation of these vaccine strains is 

 attributable to their inability to produce para-aminobenzoic acid.

 For genetically-engineered microorganisms, the phenotypic effect of 

 any genetic modification(s), either gene insertions or deletions, should 

 be thoroughly assessed. This includes but is limited to the following: 

 1) the function of the gene located at the insertion site; 2) the 

 modification to the donor genes; 3) the molecular properties of the 

 regulatory elements; and 4) the phenotypic effect of any marker genes 

 (e.g., the E. coli lacZ gene). The previous use of the recipient 

 microorganism, the donor gene(s), insertion site(s), or any gene 

 deletion(s) provides valuable information and should be documented. 

 One should not assume that certain genetic modifications will result in 

 the expected effect. 

vi. Genetic stability

 The genetic stability of the vaccine microorganism in vitro should be 

 evaluated at the highest passage level to be used in production of the 

 vaccine. If stable, it suggests that the safety characteristics of the 

 vaccine microorganism will not be altered as a result of manipulations 

 during the manufacturing process. 

 Studies to evaluate the genetic stability of the microorganism in vivo

 provide significant safety information, but are not generally required.

 

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vii. Phenotypic stability

 The phenotypic stability of the vaccine microorganism provides the 

 definitive answer to the stability of the vaccine in production or when 

 injected in the host animal. 

viii. Alteration of tissue tropism

 Any alteration in tissue tropism should be reported. Changes in tissue 

 tropism may allow the organism to shed in new ways, or there may be 

 an alteration in its pathogenicity.

ix. Effect of overdosing

 Overdosing is a standard safety test that confirms the attenuation of the 

 vaccine microorganism. Any pathogenic effects should be identified.

b. Non-Target animal safety

 Safety studies in non-target animal species should be considered when the 

 vaccine microorganism sheds and can potentially disperse in the environment. 

i. Susceptible non-target animals and probability of their exposure

 Susceptible non-target hosts should be identified. Any differences 

 between the vaccine microorganism and the parent should be documented.

ii. Virulence in non-target animals (susceptible non-target animals)

 

iii. Possible outcome of non-target animal exposure

 The possible outcome of non-target animal exposure should be assessed. 

 If no experiments were conducted with the recombinant agent, 

 information on the effect of the parent organism should be discussed.

2. Public Health Safety

a. Probability of human exposure

 The potential for human exposure, through both direct and indirect routes should 

 be identified.

b. Expected pathogenicity of the parent microorganism in humans

c. Expected virulence of the vaccine microorganism in humans:

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d. Possible outcome of human exposure

 Potential safety hazards to public health should be identified and assessed.

3. Environmental Safety

a. Shed/Spread capabilities

b. Horizontal gene transmission/recombination potential

c. Host/Range specificity

d. Survivability of the microorganism in the environment

e. Potential for transmission to invertebrates

f. Physical and/or chemical factors affecting dispersal in the environment

g. Adverse ecological effects

B. Release Assessment Prior to a Proposed Field Safety Trial

 The safety characteristics of the vaccine microorganism must be evaluated within the context

 of the target environment. Thus, the release assessment consists of a comprehensive 

evaluation of the proposed release so as to determine: 1) the location and characteristics of 

the release site; 2) the test dose and total amount of the experimental biologic to be used in the 

proposed study; 3) the frequency and duration of exposure to the test material; 4) potential 

escapes into occupational, residential, or outdoor environments; and 5) the individuals, 

populations, or ecosystems that will be, or may be, exposed to the experimental biologic.

 1. Environmental Release

a. Location of test site

 The exact location of the test site is identified. For proposed commercial uses, 

 the types of the conditions under which the vaccine will be used are identified; 

 e.g., unlimited commercial distribution and use, restricted for use by 

 veterinarians only, small animal veterinary hospitals, commercial poultry 

 houses, etc.

b. Characteristics of the test site

 A description of the test site is provided, including relevant geographical and 

 environmental information. The area surrounding the test site is also described, 

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 including the presence of non-target animal species. The condition of the test 

 site should be documented, as well as previous studies conducted on the test 

 site.

c. Personnel

 The personnel conducting the study are identified, including their 

 qualifications, training, and specific role in the study. Appropriate safeguards, 

 education, and training are provided as needed.

d. Experimental design

 The objectives of the release are identified. For small-scale field tests, the 

 protocol of study should include the following information, as appropriate: 1)

 the number of animals; 2) a description of the animals; 3) the route of 

 administration; 4) the dose; 5) the total amount of test material; 6) frequency 

 and duration of exposure; 7) the method of disposing of waste; 8) 

 decontamination of the test site.

i. animals

ii. vaccine

iii.vaccination

iv. total doses of test material

v. method of disposing of waste

vi. decontamination of the test site

e. Potential for escape and dispersal

 The potential for escape and dispersal from the release site should be assessed. 

 Possible exposure to the area surrounding the test site should be considered and 

 evaluated, including the probability of non-target animal exposure.

f. Potential for establishment in the environment

 The habitability of the test site and/or environments for the introduced vaccine 

 microorganism is appraised. The following environmental characteristics are

 evaluated, as appropriate: 1) the presence of other biological organisms; 2) the 

 nutrient status; 3) physicochemical factors; 4) the presence of toxic chemicals 

 and metabolites.

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g. Monitoring

 Appropriate methods and procedures for monitoring the released vaccine 

 microorganism in and around the test site should be identified prior to initiating 

 the study. The monitoring methods should be sensitive and specific. The 

 frequency of the monitoring should be identified. Provisions for recording the 

 results of the monitoring should be in place.

h. Contingency plans in case of adverse event

 The sponsor of the proposed study should identify contingency plans in case an 

 adverse event occurs. Contingency plans should include procedures for 

 terminating the study as quickly as possible, and identify methods to stop the 

 shed, spread, or dispersal of the vaccine microorganism once released in the 

 environment.

C. Risk Characterization

 Risk Characterization integrates the results of the hazard identification and the release

assessment into a risk statement that includes: 1) a likelihood rating; 2) a consequence 

rating; 3) a risk rating; and 4) a discussion of risk. Each likelihood and consequence rating 

is qualified by a Degree of certainty rating and includes a justification for the rating. The 

justifications for the ratings consist of identifying the applicable sections in the hazard 

identification and the release assessment that support the assigned rating. The risk rating is 

based upon the likelihood, consequence, and degrees of certainty ratings.

1. Likelihood Rating

 Likelihood ratings are assigned for animal safety, public safety, and 

 environmental safety based on the following criteria:

Low = An adverse event is unlikely to occur

Medium = An adverse event could possibly occur

High = An adverse event will most probably occur

2. Consequence Rating

 Consequence ratings are also assigned for animal safety, public safety, and 

 environmental safety based on the following criteria:

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Low = The consequences if the adverse event occurs will 

not be severe (the adverse event is self-limiting and 

would have negligible impact).

Medium = The consequences if the adverse event occurs is 

moderately severe (the adverse event will have an 

impact, but it is not permanent, and can be treated).

High = The consequences if the adverse event occurs are 

severe (the adverse event will have an impact, is 

permanent, and can not be treated).

3. Degree of Certainty Rating

 Each likelihood and consequence rating is qualified by a degree of certainty 

 rating that is based on the following criteria:

Certain = The rating is supported by direct scientific evidence.

Moderately = The rating is supported by indirect scientific 

Certain evidence.

Uncertain = The rating is not supported by scientific evidence.

4. Calculating the Expected Risk

 Numerical values have been assigned to the likelihood, consequence, and degree of 

 certainty ratings described in Table 2 (page 12). Each numerical value rating was 

 derived from the importance placed on the rating of each category. The assigned 

 numerical values are weighed to place emphasis on the severity of expected risk. 

 These values reflect the scientific and professional judgment of the applicant and will 

 be reviewed by the CVB. To determine the expected risk, the numerical values are 

 multiplied.

 The numerical values assigned to the "Degree of Certainty" reflect the level of 

 uncertainty associated with the risk ratings. The need for two different rating systems 

 reflects the reality of how uncertainty is perceived when handing risk. A low risk with 

 a high degree of certainty is of less concern than a low risk which shows a high degree 

 of uncertainty; a high risk with a high degree of certainty is of more concern than a 

 high risk which shows a high degree of uncertainty.

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 This is easy to understand by using an analogy about risk. A pedestrian is less likely to 

 cross the road if he is convinced he is going to be hit by a car than if he is not sure that 

 he will be hit by a car (high risk with a high degree of certainty is of more concern

 than a high risk which shows a high degree of uncertainty). However, the same 

 pedestrian is more likely to cross the road if he is convinced that he is not going to be 

 hit by a car than if he thinks that he might be hit by a car (low risk with a high degree 

 of certainty is of less concern that a low risk which shows a high degree of 

 uncertainty). The use of the two rating systems (one a reciprocal of the other) reflects 

 this perception of risk.

5. Risk Ratings

 The risk ratings are based upon the likelihood, consequence, and degrees of certainty 

 ratings and the expected risk for each category (Table 2, Page 12). A total of 81 

 rating combinations are possible; e.g., Likelihood Low-Moderately Certain, 

 Consequence Low-Moderately Certain (Table 3, Page 13). Each combination has 

 been assigned a risk rating of low, medium, or high. The assigned ratings were 

 weighed to place emphasis on the severity of the expected risk. Again, the severity of 

 the risk reflects the professional judgment of the applicant and will be reviewed by the 

 CVB. The low, medium, or high risk ratings are defined for the purpose of decision-

 making, as follows:

Low=Acceptable risk - very little concerns are associated with the proposal (does 

not justify denying the proposal)

Medium=Unacceptable risk - moderate concerns are associated with the proposal 

(either identify valid mitigative procedures or deny the proposal).

High=Unacceptable risk - major concerns are associated with the proposal (deny 

the proposal).

 A. Animal safety – example

Likelihood Rating: Low (LL)

Degree of Certainty Rating: Certain (C)

Consequence Rating: Low (CL)

Degree of Certainty Rating: Certain (C) 

Expected Risk Rating: 1.0000

Risk Characterization: LL.C.CL.C

Risk Rating: L

Justification for Rating: (cite relevant Sections of Risk Assessment)

(i) Conclusion and discussion of risk

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 B. Public health safety – example

Likelihood Rating: Low

Degree of Certainty Rating: Certain

Consequence Rating: Low

Degree of Certainty Rating: Certain

Expected Risk Rating: 1.0000

Risk Characterization: LL.C.CL.C

Risk Rating: L

Justification for Rating: (cite relevant Sections of Risk Assessment)

(i) Conclusion and discussion of risk

 

C. Environmental safety – example

Likelihood Rating: Low

Degree of Certainty Rating: Certain

Consequence Rating: Low

Degree of Certainty Rating: Moderately Certain

Expected Risk Rating: .7500

Risk Characterization: LL.C.CL.MC

Risk Rating: L

Justification for Rating: (cite relevant Sections of Risk Assessment)

(i) Conclusion and discussion of risk

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Table 1: Veterinary Biologics Risk Analysis

______________________________________________________________________________

RISK ANALYSIS FOR VETERINARY BIOLOGICS

I. Objective/Proposal

II. Summary of Information Format (SIF) providing characterization of the vaccine 

microorganism (http://www.aphis.usda.gov/vs/cvb/lpd/sifs.htm)

A. Microbiological/Molecular properties

B. Biological properties

III. Risk assessment

A. Hazard identification

1. Animal safety

2. Public health safety

3. Environmental safety

B. Release assessment

C. Risk characterization

IV. Risk management

A. Contained release – not applicable for Field Safety Trials

B. Environmental release

V. Risk communication

A. Finding of No Significant Impact (FONSI)

B. Publication in the Federal Register announcing availability of an environmental 

assessment and CBI-deleted risk analysis

______________________________________________________________________________

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Table 2: Calculating the Expected Risk

 

VALUE RATINGS 

Likelihood (L)

Low (L)LL = 1.00

 

Medium (M)LM = 0.50

High (H)LH = 0.10 

 

Consequence (C)

Low (L)CL = 1.00

Medium (M)CM = 0.10

High (H)CH = 0.01

If the Likelihood rating is Medium or High and the Consequence rating is also Medium or High 

use Degree of Certainty Ratings I; for all other combinations use Degree of Certainty Ratings II.

Degree of Certainty Ratings I

Certain (C) C = 0.50

 

Moderately Certain (MC)MC = 0.75

 

Uncertain (U) U = 1.00 

 

Degree of Certainty Ratings II

Certain (C) C = 1.00

 

Moderately Certain (MC)MC = 0.75

 

Uncertain (U) U = 0.50 

EXPECTED RISK

[(likelihood) x (degree of certainty)] x [(consequence) x (degree of certainty)] = Risk Rating 

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Table 3: Risk Ratings

 

Risk Expected Risk Risk Expected Risk

Characterization Risk Rating Characterization Risk Rating 

----------------------------------------------------------------- -----------------------------------------------------------------

LL.C.CL.C. 1.0000 L LM.C.CM.C. .0125 M 

LL.C.CL.MC. .7500 L LH.U.CM.U. .0100 M

LL.MC.CL.C. .7500 L LL.C.CH.C. .0100 M

LL.MC.CL.MC. .5625 L LH.MC.CM.U. .0075 M

LL.C.CL.U. .5000 L LH.U.CM.MC. .0075 M

LL.U.CL.C. .5000 L LL.C.CH.MC. .0075 M

LM.C.CL.C. .5000 L LL.MC.CH.C. .0075 M

LL.MC.CL.U. .3750 M LH.MC.CM.MC. .0056 M

LL.U.CL.MC. .3750 M LL.MC.CH.MC. .0056 M

LM.C.CL.MC. .3750 M LH.C.CM.U. .0050 M 

LM.MC.CL.C. .3750 M LH.U.CM.C. .0050 M

LM.MC.CL.MC. .2813 M LL.C.CH.U. .0050 M

LL.U.CL.U. .2500 M LL.U.CH.C. .0050 M

LM.C.CL.U. .2500 M LM.U.CH.U. .0050 M

LM.U.CL.C. .2500 M LH.C.CM.MC. .0038 M

LM.MC.CL.U. .1875 M LH.MC.CM.C. .0038 M

LM.U.CL.MC. .1875 M LL.MC.CH.U. .0038 M

LM.U.CL.U. .1250 M LL.U.CH.MC. .0038 M

LH.C.CL.C. .1000 M LM.MC.CH.U. .0038 M

LL.C.CM.C. .1000 M LM.U.CH.MC. .0038 M

LH.C.CL.MC. .0750 M LM.MC.CH.MC. .0028 M

LH.MC.CL.C. .0750 M LH.C.CM.C. .0025 M

LL.C.CM.MC. .0750 M LL.U.CH.U. 0025 M

LL.MC.CM.C. .0750 M LM.C.CH.U. .0025 M

LH.MC.CL.MC. .0563 M LM.U.CH.C. .0025 M

LL.MC.CM.MC. .0563 M LM.C.CH.MC. .0019 H

LH.C.CL.U. .0500 M LM.MC.CH.C. .0019 H

LH.U.CL.C. .0500 M LM.C.CH.C. .0013 H

LL.C.CM.U. .0500 M LH.U.CH.U. .0010 H

LL.U.CM.C. .0500 M LH.MC.CH.U. .0008 H

LM.U.CM.U. .0500 M LH.U.CH.MC. .0008 H

LH.MC.CL.U. .0375 M LH.MC.CH.MC. .0006 H

LH.U.CL.MC. .0375 M LH.C.CH.U. .0005 H

LL.MC.CM.U. .0375 M LH.U.CH.C. 0005 H

LL.U.CM.MC. .0375 M LH.C.CH.MC. .0004 H

LM.MC.CM.U. .0375 M LH.MC.CH.C. .0004 H

LM.U.CM.MC. .0375 M LH.C.CH.C. .0003 H

LM.MC.CM.MC. .0281 M

LH.U.CL.U. .0250 M

LL.U.CM.U. .0250 M

LM.C.CM.U. .0250 M

LM.U.CM.C. .0250 M

LM.C.CM.MC. .0188 M

LM.MC.CM.C. .0188 M 

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